Ultrastructural abnormalities of placental villi in placentae from pregnancies complicated by intrauterine fetal growth retardation: their relationship to decidual spiral arterial lesions.

An ultrastructural study has been made of villi adjacent to decidual spiral arteries exhibiting varying degrees of luminal occlusion in placentae from cases of intrauterine growth retardation. Partially occluded spiral arteries are associated with placental villous syncytiotrophoblast exhibiting extensive budding of surface microvilli, vacuolation of the cytoplasm, clumping of nuclear chromatin and a thickening of the underlying basement membrane. Marked degeneration of the syncytium is present in association with severely occluded spiral arteries. In contrast, the capillary endothelium of the villus retains a normal structure despite degenerative changes in villous Langhan's and stromal cells. The most extensive pathological changes in the placental villi are found distal to completely occluded spiral arteries and consist of complete necrosis of the syncytium and underlying fetal blood vessels, These findings suggest that the occlusive lesions in the maternal uterine vasculature may be the major cause of the infarction and impairment of placental function found in pregnancies complicated by fetal growth retardation.